Abstract: In last century, extensive areas of native vegetation in the Miyaluo forest area of Western Sichuan were converted into agricultural land and forestland. To assess the effects of land use change on soil organic carbon (SOC) and microbial biomass carbon (MBC), soil samples were taken from Abies faxoniana wildwood, Picea likiangensis var. balfouriana plantations established in 1960s and 1980s, and cropland, and their SOC and MBC contents were determined. The results showed that A. faxoniana wildwood had the highest SOC and MBC contents, followed by the P. likiangensis var balfouriana plantations established in 1960s and 1980s, and cropland. The SOC content was 83%, 53% and 52% lower, and the MBC content was 23%, 25% and 21% lower in cropland than in wildwood and in the plantations established in 1960s and 1980s, respectively. SOC and MBC contents decreased with increasing soil depth. There existed significant correlations of these two indices with soil total N, hydrolysable N and available P, indicating that both SOC and MBC could be used as the important indicators to measure the changes of soil quality.

Key words: Ecosystem, Purifying service, Value